Herb doesnt' need a container over 5 gallons. Hopefully this is your last transplant since weed doesnt like its root structure being disturbed much. So the less times transplanted, the better off you'll be. Glad to hear that they didnt show any signs of stress. You're lucky. Depending on your geography (climate) and strain of herb the plant will naturally know when to start flowering. Usually, when the natural light starts getting less (days becoming shorter) after Summer Solstice (June 22nd). It generally takes about 1-2 weeks for the marijuana plant to register the light difference change. The shorter days are an idicator for weed to start flowering and reproduce. You're plant potentially has another 2 1/2-3 weeks of vegetative growth. So, you may see a larger increase in size...Better hide your plant! Remember, not all plants grow at the same rate of speed/height even if its the same strain, so things vary.
Hope this helps, and good luck! Send pics.